185. 部门工资前三高的员工

Employee 表包含所有员工信息，每个员工有其对应的 Id, salary 和 department Id 。

+----+-------+--------+--------------+
| Id | Name  | Salary | DepartmentId |
+----+-------+--------+--------------+
| 1  | Joe   | 70000  | 1            |
| 2  | Henry | 80000  | 2            |
| 3  | Sam   | 60000  | 2            |
| 4  | Max   | 90000  | 1            |
| 5  | Janet | 69000  | 1            |
| 6  | Randy | 85000  | 1            |
+----+-------+--------+--------------+

Department 表包含公司所有部门的信息。

+----+----------+
| Id | Name     |
+----+----------+
| 1  | IT       |
| 2  | Sales    |
+----+----------+

编写一个 SQL 查询，找出每个部门工资前三高的员工。例如，根据上述给定的表格，查询结果应返回：

+------------+----------+--------+
| Department | Employee | Salary |
+------------+----------+--------+
| IT         | Max      | 90000  |
| IT         | Randy    | 85000  |
| IT         | Joe      | 70000  |
| Sales      | Henry    | 80000  |
| Sales      | Sam      | 60000  |
+------------+----------+--------+ 

例1：

# Write your MySQL query statement below
Select d.Name as Department, e.Name as Employee, e.Salary 
from Department d, Employee e 
where b.DepartmentId = d.Id and (
    Select count(distinct Salary) From Employee where DepartmentId=d.Id and Salary > e.Salary
)<3
order by Department     

例2：

# Write your MySQL query statement below
SELECT d.Name AS Department, e1.Name AS Employee, e1.Salary
FROM Employee e1 JOIN Department d ON e1.DepartmentId = d.Id
WHERE 3 > (SELECT COUNT(DISTINCT e2.Salary) FROM Employee e2
           WHERE e2.Salary > e1.Salary AND e1.DepartmentId = e2.DepartmentId);

例3：

# Write your MySQL query statement below          
SELECT D1.Name Department, E1.Name Employee,  E1.Salary
FROM Employee E1, Employee E2, Department D1
WHERE E1.DepartmentID = E2.DepartmentID
AND E2.Salary >= E1.Salary 
AND E1.DepartmentID = D1.ID      
GROUP BY E1.Name
HAVING COUNT(DISTINCT E2.Salary) <= 3
ORDER BY D1.Name, E1.Salary DESC;